U n.
f long oo, as in tool, and short oo, as in wood, answering to the French ou in tour. Etymologically U is most closely related to o, y (vowel), w, and v; as in two, duet, dyad, twice; top, tuft; sop, sup; auspice, aviary. See V, also O and Y. See Guide to Pronunciation, §§ 130-144.